Streaming movies and television shows, uploading video to Facebook, playing games and downloading music all have one thing in common: data.

If you're not connected to Wi-Fi, you could be in for some shocking data charges on your next bill.

Wasyl Nyszczej received a bill $600 higher than usual and he blames a latent feature enabled on his daughter's Apple iPhone: Wi-Fi assist.

The feature came out in 2015 with Apple's iOS 9 software upgrade, allowing iPhones and iPads to seamlessly switch to cellular data when the Wi-Fi signal is weak. It's enabled by default, unless you manually switch it off and it could be costly.

Nyszczej's service provider, Verizon, texted alerts to him about his usage. He warned his daughter Erika to be careful.

"She assured me she's on Wi-Fi all the time," Nyszczej said, "you can get into trouble if you're not careful."

We asked Mashable's deputy Tech Editor, Damon Beres, to show us a few tweaks to save a lot of money.

First you can start by finding the data hogs:

Start by opening Cellular in your iPhone Settings or data usage on Android.

Identify the apps eating way into your cellular plan and turn them off.

Sharing video on Facebook, Instagram and Twitter can take a major toll when you're out. If possible, wait until you get home and connect to Wi-Fi before watching or uploading video.

Next, be cautious playing games that require an internet connection. If you have a poor signal, some constantly connect to the Internet to update.

Streaming video and music can also use a ton of data.

Apps like Netflix and Spotify have settings that can reduce media quality to keep data charges down when not connected to Wi-Fi.

When we contacted Verizon, Nyszczej said they cut his overage charges in half.

The big takeaway to avoid this problem is to disable Wi-Fi assist. It's located under settings-cellular and at the bottom of the page.

You won't have the smoothest experience when connected to the internet but you also won't go way over your monthly allowance.